1. Technical Field
The present invention generally relates to motor vehicles. More particular, the present invention relates to a overrunning clutch assembly for an automatic transmission of a motor vehicle.
2. Discussion
A conventional automatic transmission includes a hydrodynamic torque converter to transfer engine torque from an engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The automatic transmission also includes frictional units, typically referred to as clutches, which couple the rotatable input member to one or more members of a planetary gear set. Other frictional units, typically referred to as brakes, hold one or more members of the planetary gear set stationary during the flow of power. Examples of such automatic transmissions are disclosed in commonly assigned U.S. Pat. No. 4,875,391 to Leising et al. and U.S. Pat. No. 5,800,303 to Benford, which are hereby incorporated by reference as if fully set forth herein.
Such transmissions also typically provide for one or more overrunning clutches in order to improve shift quality. Examples of overrunning clutches for automatic transmissions include ratchet type clutches and traction locking clutches such as a roller ramp or sprag clutch. Typically, overrunning clutches generally include an inner race and an outer race. A discussion of such clutches is disclosed in U.S. Pat. No. 5,070,978 to Pires and U.S. Pat. No. 5,511,642 to Klotz et al., which are hereby incorporated by reference as if fully set forth herein. U.S. Pat. No. 5,511,642 discloses an overrunning clutch having an inner race operatively connected to a brake assembly, an outer race operatively connected to a transmission housing, and a structure disposed between the inner race and outer race for allowing the brake assembly to rotate in only one direction. The particular structure disposed between the inner race and the outer race comprises a plurality of rollers.
Conventional planetary gear assemblies incorporate helical gearing. As a result, significant axial loads or thrust loads are generated by the various planetary gear sets during operation of the automatic transmission. These thrust loads are transmitted to the transmission housing through various components. Through prolonged normal use, as well as through certain extreme operating conditions, certain components of conventional transmissions may prematurely fail from the thrust loads. For example, extreme thrust loads may cause the outer race of an overrunning clutch to axially shift relative to the inner race. If this occurs, the rollers between the inner and outer races may fall out of position.
Thus, a need remains in the art for an overrunning clutch assembly capable of reacting thrust loads during prolonged normal use of an automatic transmission, as well as during extreme operating conditions.